1. Field of the Invention
The present invention relates to a method of recording and reproducing picture information on and from a recording medium such as a video disc, a digital audio disc, and so on, and a recording medium, and also relates to a recording medium playing apparatus.
2. Description of Background Information
In recording and reproducing contents of a movie source (or film source, in other words) on and from a recording medium such as a video disc, it is general to originally superimpose characters such as the translation of dialogues on the picture. Since the characters obtained by this conventional method are always displayed without regard to the user's will, such a display can be annoying for viewers in some occasions. Also, there have been a problem that it is necessary to prepare a master disc separately for each of different languages.
Accordingly, it is conceivable to adopt a method in which characters are coded by means of the so-called closed caption system and the coded signal is inserted in portions of a video format signal containing the information obtained from the movie (film) source which do not appear on the display screen, such as the fly-back time portions, and in reproduction, the characters are reproduced by means of a decoder prepared for that purpose. With this method, the display of characters can be enabled at need by an on-off control of the decoder of that purpose.
However, since the amount of data which can be inserted is relatively small in the closed caption method, and it is possible to display superimposed characters only in one language. Therefore, there still remains the problem that master discs must be prepared respectively for each language.
On the other hand, a system is proposed in which picture information is recorded and reproduced in the form of the subcode on and from a digital audio disc. The subcode is made up of eight subcode bits, and bit groups forming the subcode are divided into eight channels denoted respectively by letters P, Q, R, S, T, U, V, and W. In the method in which the picture information is recorded and reproduced in the form of subcode, data corresponding to picture information is configured such that a symbol is formed by 6 bits of channels R through W out of the 8 bits forming the subcode, and 98 symbols are treated as one block, as illustrated in FIG. 1. Two symbols in the 98 symbols are used as a sync signal, and 24 symbols obtained by dividing the remaining 96 symbols, by four are treated as a minimum unit of data, i.e. a "pack", which constitutes one instruction of picture processing.
More specifically, the first symbol (referred to as symbol 0 hereinafter) of the 24 symbols shows one of several modes. A symbol 1 following this symbol 0 forms instruction which indicates the sort of the instruction. Symbols 2 and 3 following the symbol 1 constitute a parity Q which is an error correction code. Symbols 4 through 19 following the parity Q constitute a data field, and include information such as color information. Finally, symbols 20 through 23 following the data field constitute a parity P which is an error correction code for protecting the information in the "pack".
On the other hand, there are four modes, i.e. "zero mode", "line-graphics mode", "TV-graphics mode", and "user's mode". The "zero mode" is provided for a case where no operation is required for pictures on the display screen, that is, the original image is to be maintained, and all data in the "pack" are 0 for this mode.
The "line-graphics mode" is provided for such a case that a liquid crystal display is provided on the front face of the player, to display notes such as an explanation of a music selection. As shown in FIG. 2, a picture area being long sideways is formed by pixels which are arranged in 288 columns and 24 rows. In other words, each row includes 288 pixels and each column includes 24 pixels. The term "pixel" stands for the minimum display element of a picture, and it is general that the picture processing is performed by using picture composing units designated as "fonts" each of which is made up of pixels divided into 6 columns and 12 rows.
The number of "fonts" which can be displayed in the "line-graphics mode" is 48 in the lateral direction, and 2 in the column direction, and this area is designated as "screen area". For providing the scroll function, in line of "fonts" is added to the upper and lower outer peripheries and the right and left peripheries of the Screen area, to form a picture area having 50 "fonts" in the direction of row, and 4 "fonts" in the direction of column. The subcode is formed so that the picture processing is performed by using a memory having addresses each corresponding to each pixel in this picture area. In addition, the area outside the "screen area" is designated as "border".
The "TV-graphics mode" is a mode for displaying images on the TV screen, and a picture is formed by pixels arranged in 192 rows and 288 columns as illustrated in FIG. 3. The number of "fonts" which can be displayed in the "TV-graphics mode" is 48 in the direction of row, and 16 in the direction of column. Also in this "TV-graphics mode", the subcode is formed so that the picture processing is performed by using a memory having addresses each of which corresponds to each pixel in a picture area having 50 "fonts" in the direction of row, and 18 "fonts" in the direction of column, made by adding a line of "fonts" to the upper end and lower peripheries as well as the right and left outer peripheries of the "screen area".
As instructions for the picture processing, there are an instruction for painting out the whole picture area by one certain color, an instruction for drawing a picture in one "font" on the screen by using two different colors, an instruction for moving the whole picture upward or sideways, and so on.
Additionally, in the 8-bit groups forming the subcode, the Q bits forming the channel Q include time information corresponding to the track length to a certain position of each information data which is recorded from the beginning of the program area of CD, and form address time data which can be used as positional data representing the recording position. On the other hand, the P bits forming the channel P form data including information relating to a pause between two music selections.
In the above-described system of recording and reproducing picture information as subcode, the time period necessary for displaying a picture of one "font" is about 3.3/1000 second, and about 2.5 seconds are necessary for displaying 48.times.16 characters. This means that data corresponding to 48.times.16 characters can be recorded in a track section which the pickup traces for 2.5 seconds, and such a recording capacity is sufficient for recording dialogues translated in several languages. However, with conventional recording and reproducing methods using the subcode explained so far, the picture obtained from the subcode such as characters is displayed using the whole area of the screen. Therefore it was not possible to view the picture obtained from the subcode such as characters, simultaneously with the picture obtained from the video format signal containing information obtained from a source such as a movie film, by superimposing the picture obtained from the subcode as a superimposed dialogue.